Boeing made a big deal about the 787 using the green ISO 'running man' exit signs vs. the traditional white and red EXIT signs. One of the reasons was to reduce the number of bilingual signs needing to be made depending on the airline's country.

I was therefore surprised when I flew on UA's 787 that they have the white and red EXIT signs instead.

Anyone know the reason why? Is this something Boeing installs at UA's request, or does UA have to modify this post-delivery?

I noticed in this video does show one of UA's first 787s with the running man signs:
I doubt this is a US regulatory issue as Boeing sought FAA approval to use these signs during the 787 development process, and both AA's 787s and DL's new A321s use the running man signs.